TWI833116B - Optical interference tomography device and optical interference tomography method - Google Patents

Abstract

The present invention provides an optical interference tomography apparatus that is not prone to deviation in tomographic images even if it is portable and can perform tomography of a wide range at once, and an optical interference tomography method using the same. The optical interference tomography apparatus of the present invention includes an objective lens for focusing light from a light source on a sample, and is based on the reflected light from the sample, that is, the sample light, and the reference provided between the objective lens and the sample. The reflected light from the surface is the interference of the reference light, and the tomography of the above-mentioned sample is performed, and both the above-mentioned sample light and the reference light pass through the above-mentioned objective lens, and the above-mentioned objective lens is an Fθ lens.

Description

Optical interference tomography device and optical interference tomography method

The invention relates to an optical interference tomography device and an optical interference tomography method.

Optical Coherence Tomography (OCT) is mainly used in the medical field for tomography of biological organs such as eyeballs.

As an optical interference tomography device, the light from the light source is generally divided by a spectroscope, etc., and is irradiated to the sample and the reference mirror respectively to obtain reflected light, and the interference of the reflected light passing through the respective optical paths is used to perform tomography ( For example, refer to Patent Document 1). [Prior technical literature] [Patent Document]

Patent Document 1: Japanese Patent Application Publication No. 2011-104127

[Problem to be solved by the invention]

An object of the present invention is to provide an optical interference tomography apparatus that is not prone to deviation in tomographic images even if it is portable and can perform tomography of a wide range at once, and an optical interference tomography method using the same. [Technical means to solve the problem]

The present invention relates to an optical interference tomography apparatus, which is provided with an objective lens that condenses light from a light source on a sample, and is based on the reflected light from the sample, that is, the sample light, and the space between the objective lens and the sample. The reflected light from the set reference surface is the interference of the reference light, and the tomography of the above sample is performed, and Both the above-mentioned sample light and the reference light pass through the above-mentioned objective lens, The above objective lens is an Fθ lens.

The optical interference tomography apparatus is preferably configured so that the tomography can be performed with the distance between the reference surface and the sample being 0 to 3 cm.

The reference surface is preferably a flat surface of a reference member including at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz, and sapphire.

It is preferable that both the sample light and the reference light are generated from the light from the light source passing through the objective lens.

The above-mentioned interference is preferably a Fezuo-type interference.

The optical interference tomography apparatus preferably further includes a circulator that outputs light from the light source to the side of the objective lens, and outputs the sample light and reference light passing through the objective lens to detect the sample. light and reference light on the detector side.

The optical interference tomography apparatus preferably further includes a coupler that splits the light from the light source into split light 1 for generating the sample light and reference light, and a split light 1 for removing the DC component of the interference signal. Split light 2, and the intensity ratio of split light 1 and split light 2 is 90:10~99:1.

The above-mentioned optical interference tomography apparatus is preferably configured in such a manner that a user can carry the part provided with the above-mentioned objective lens and perform the above-mentioned tomography.

Preferably, the portable part equipped with the objective lens and the non-portable part are connected via an optical fiber. The light from the above-mentioned light source, the above-mentioned sample light and the reference light are transmitted through the above-mentioned optical fiber.

Preferably, the length of the optical fiber is 3 m or more, and the optical interference tomographic image is obtained when the temperature difference between the surrounding environment of the part carrying the objective lens and the part not carrying the objective lens is 1°C or more. The deviation is less than 100 μm.

The present invention also relates to an optical interference tomography method using any of the above-mentioned optical interference tomography devices. [Effects of the invention]

According to the present invention, it is possible to provide an optical interference tomography apparatus that is less likely to cause deviation in tomographic images even if it is portable and can perform tomography of a wide range at once, and an optical interference tomography method using the same.

In the medical field, an optical interference tomography (OCT) device using a Michelson interferometer as shown in Figure 1 is generally used. In the OCT device 10 of FIG. 1 , the light output from the light source 11 is split by the coupler 12 to generate reference light that passes through the optical path including the circulator 13 and the reference mirror 14 , and passes through the optical path including the circulator 15 and the sample 16 The sample light. The reference light and the sample light are coupled by the coupler 17 , and the interference signal is detected by the photodetector 18 .

In the medical field, usually, a detector with a sample optical path and an OCT device body (casing) with a reference optical path are installed close to each other and used in the same room. On the other hand, in the industrial field, etc., it is sometimes required to carry a detector and photograph an object located far away from the OCT device body (casing), such as outdoors. In this case, in the Michelson-type OCT device in Figure 1 where the sample light and the reference light pass through their respective optical paths, there are the following problems: the environment in which the sample light path (detector) and the reference light path (body) are placed ( Temperature, etc.) are prone to differences, and due to changes in optical path length, the deviation (offset) of the obtained tomographic image will become larger.

In addition, there is also the following problem: OCT devices used in the medical field focus on tomographic imaging of a very narrow range such as the eyeball with high precision, and are difficult to apply to applications that require tomography of a wide range at once. In the field of photography.

The present inventors conducted active research and found that by passing both the sample light and the reference light through an objective lens and using an Fθ (F Theta) lens as the objective lens, the above problems can be solved, and the OCT device of the present invention was completed.

Hereinafter, the present invention will be described in detail.

The present invention relates to an optical interference tomography (OCT) apparatus, which is provided with an objective lens that condenses light from a light source on a sample, and is based on the reflected light from the sample, that is, the sample light, and the light from the above-mentioned objective lens and the above-mentioned sample. The interference of the reference light, which is the reflected light from the reference surface provided between the samples, is used to perform tomography of the sample, and both the sample light and the reference light pass through the objective lens, which is an Fθ lens.

In the OCT device of the present invention, both the sample light, which is the reflected light from the sample to be photographed, and the reference light, which is the reflected light from the reference surface, pass through the objective lens. With this configuration, even when the part equipped with the objective lens (such as a detector) is made portable, there will be no environmental difference between the sample optical path and the reference optical path, so the deviation of the tomographic image obtained will be small. . Furthermore, the sample light and the reference light are incident from the sample side of the objective lens and emitted to the light source side.

The above-mentioned sample light and reference light are generated from light from a light source. The light from the light source passes through the objective lens of the OCT device of the present invention and is focused on the sample. The reflected light from the sample is regarded as the sample light. In addition, part of the light from the light source is reflected by a reference surface provided between the objective lens and the sample, and becomes reference light. It is preferable that the sample light and the reference light are both generated from the light from the light source passing through the objective lens. Compared with the situation where the sample light and the reference light are generated separately from the light split in front of the objective lens like the conventional Michelson type OCT device, the environmental difference between the sample light path and the reference light path can be reduced, and the obtained light can be further reduced. Deviation of tomographic images.

The objective lens provided in the OCT device of the present invention is an Fθ lens. With this configuration, tomographic imaging of a wide range can be performed at once. The above-mentioned Fθ lens is a lens in which light incident at an angle θ with respect to the optical axis of the lens is emitted from the optical axis of a plane perpendicular to the optical axis at the focal point to a position fθ when the focal distance of the lens is set to f.

The above-mentioned Fθ lens may be a telecentric Fθ lens or a non-telecentric Fθ lens. The telecentric Fθ lens is an Fθ lens designed with the main ray parallel to the optical axis of the lens. It is better in that it can obtain high-precision tomographic images even if the distance between the lens and the sample changes.

In the OCT device of the present invention, the light passing through the objective lens does not need to be telecentrically incident on the sample. However, in order to obtain a more precise tomographic image, it is preferable to be incident as close to the telecentricity as possible. Configure the objective lens as above.

The reference plane is preferably provided between the objective lens and the sample and perpendicular to the optical axis of the objective lens. The above-mentioned reference surface only needs to be a surface that reflects at least a part of the light from the above-mentioned light source. However, in order to easily configure the sample light and the reference light through a common optical path, it is preferably a surface that "penetrates" the light from the above-mentioned light source. A surface that reflects part of the light from the light source. In this aspect, the light passing through the reference surface is condensed on the sample to generate sample light, while the light reflected from the reference surface becomes reference light.

The reference surface is preferably a plane of the reference member, and more preferably is the surface of the reference member on the sample side. The reference member preferably transmits part of the light from the light source and reflects part of it.

Examples of materials constituting the reference member include crystalline materials, preferably crystals that can be used for optical windows, and specific examples include MgF ₂ , quartz (SiO ₂ ), sapphire (Al ₂ O ₃ ), and CaF. _2. Crystals of BaF ₂ , LiF, ZnSe, etc. Among them, in terms of excellent chemical resistance, at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz, and sapphire is preferred. A suitable aspect is that the reference plane is a plane of a reference member, and the reference member includes at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz, and sapphire. The above-mentioned reference member is preferably not coated (for example, coated to adjust reflection).

The shape of the above-mentioned reference member only needs to be a flat shape, and may be a plate shape, a cylindrical shape, a corner prism shape, etc., but a cylindrical shape is preferred. In the case of a cylindrical shape, it does not need to be a right cylinder. Furthermore, when the reference member further has a plane other than the reference plane, the reference plane does not need to be parallel to the other plane.

The thickness of the reference member (thickness in the optical axis direction) is, for example, preferably 1 to 50 mm, more preferably 10 to 30 mm. Furthermore, when the thickness of the reference member is not fixed, it is preferable that the thickness of the thinnest part and the thickest part are both within the above range.

The above-mentioned reference member preferably satisfies the following relational expression (1). nd≧Z _max (1) (In the formula, nd represents the optical thickness of the above reference member, and Z _max represents the measurable distance.) The optical thickness is the product of the refractive index of the above reference member and the actual (geometric) thickness . The measurable distance is expressed by the following relational expression (2). Z _max =c/(4δf) (2) (In the formula, c represents the speed of light, and δf represents the frequency interval of OCT interference signal sampling.) When using a reference component that satisfies the relationship (1), based on the parameters from the above reference component The signal reflected behind the base surface (the surface opposite the reference surface) does not appear in the tomographic image (in the range corresponding to the depth exceeding 0 and not reaching Z _max ), so a higher-precision tomographic image can be obtained.

The above reference member preferably satisfies the following relational expression (3). n×WD>nd>n×Z _max (3) (In the formula, n represents the refractive index of the above reference member. WD represents the operating distance of the OCT device. nd and Z _max are as above.) The working distance (working distance) is The distance from the frontmost surface of the specimen side of the objective lens to the specimen during self-focusing. When using a reference member that satisfies relational expression (3), the intensity of the ghost image based on the rear reflection from the rear base surface of the reference member (the surface opposite to the reference surface) can be reduced, and a higher-precision tomogram can be obtained. picture. In order to further reduce the intensity of the ghost image due to rear reflection, the thickness of the reference member is preferably within a range that satisfies relational expression (3) and is thicker. Furthermore, it is also preferable that the rear base surface of the reference member is inclined relative to the reference surface. The above effect is particularly noticeable when a de-aliasing filter (low-pass filter) described below is set.

It is particularly preferable that the above-mentioned reference member satisfies the following relational expression (4). nd _{= m} good. When using a reference member that satisfies relational expression (4), the signal reflected from the rear base surface of the reference member (surface opposite to the reference surface) and the end of the tomographic image (corresponding to depth 0 or Z _max The corresponding positions) overlap, so there is less impact on the tomographic image, and a higher-precision tomographic image can be obtained.

The OCT device of the present invention may be provided with the above-mentioned reference surface (reference member).

The OCT device of the present invention is preferably configured so that the tomography can be performed with the distance between the reference surface and the sample being 0 to 3 cm. When the reference surface and the sample can be brought close to each other in this way, the operating distance becomes shorter, the noise becomes smaller, and the resolution becomes higher. In addition, the depth of the sample can be focused and clearer tomographic images of deeper depths can be obtained. Better in terms of aspects. The OCT device of the present invention uses an Fθ lens as the objective lens, so even when the distance between the reference surface and the sample is close to each other as described above, tomography can be performed with high accuracy. Of course, tomography can also be performed by making the distance between the reference surface and the sample larger than the above distance.

The above-mentioned light source can be a low-coherence light source, preferably a frequency-sweeping light source that "scans by changing the frequency (wavelength) over time." As the above-mentioned frequency scanning light source, wavelength scanning laser using a wavelength scanning filter (driving by a polygon mirror, driving by a galvanometer mirror, etc.), FDML laser, MEMS wavelength scanning light source (MEMS VCSEL, external resonance, etc.) can be used Device type MEMS Fabry-Perot laser, etc.), SGDBR laser, etc.

Examples of the light output from the above-mentioned light source include visible rays and infrared rays, and preferably near-infrared rays (NIR). As the above-mentioned light, it is preferable to use light with a wavelength of 800 to 2000 nm. Among them, in terms of the stability of the light source or the reliability of the sensor, light with a central wavelength of 940±50 nm, 1100±50 nm, 1310±50 nm, 1550±100 nm or 1750±100 nm is better. .

The OCT device of the present invention may be equipped with the above-mentioned light source.

The OCT device of the present invention performs tomography of the sample based on the interference of the sample light and the reference light. The above-mentioned interference only needs to allow both the above-mentioned sample light and the reference light to pass through the above-mentioned objective lens in principle, and is preferably a Frisot-type interference or a Milau-type interference, and is more preferably a Frisot-type interference.

Examples of types of OCT that can be used by the OCT device of the present invention include Time Domain OCT (TD-OCT), Fourier Domain OCT (Fourier Domain OCT: FD-OCT), and the like. Examples of FD-OCT include Spectral Domain OCT (SD-OCT) and Sweep Source OCT (SS-OCT). Among them, SS-OCT is preferable in terms of high sensitivity and deep measurable depth.

The OCT device of the present invention preferably further includes a collimator for converting light from the above-mentioned light source into parallel light. The collimator is preferably disposed on the optical path between the light source and the objective lens.

The OCT device of the present invention preferably further includes a scanning mirror for scanning the light from the light source that is focused on the sample. The scanning mirror is preferably disposed on the optical path between the light source and the objective lens, and more preferably is disposed on the optical path between the collimator and the objective lens.

Examples of the scanning mirror include galvanometer mirrors, polygon mirrors, MEMS mirrors, and the like. Among them, a galvanometer mirror is preferred, a single-axis or dual-axis galvanometer mirror is more preferred, and a dual-axis galvanometer mirror is even more preferred.

The OCT device of the present invention preferably further includes a driving device for driving the scanning mirror.

The OCT device of the present invention preferably further includes a circulator that outputs light from the light source to the side of the objective lens, and outputs the sample light and reference light passing through the objective lens to detect the sample light. and the reference light side of the detector. In this aspect, the sample light and reference light can be transmitted through one circulator. With this structure, compared with the case where separate circulators are provided for passing the sample light and the reference light as shown in FIG. 1 , the device can be miniaturized and the cost can also be reduced.

The above-mentioned circulator preferably has three or more ports, and more preferably has three ports.

The circulator is preferably disposed on the optical path between the light source and the objective lens, and more preferably is disposed on the optical path between the light source and the collimator. In the case of a 3-port circulator, the light from the above-mentioned light source is input from the first port located on the side of the above-mentioned light source and output from the second port located on the side of the above-mentioned objective lens. The sample light and reference light passing through the objective lens are input from the second port and output from the third port located on the side of the detector.

The OCT device of the present invention preferably further includes a detector (also referred to as detector (1)) for detecting the sample light and reference light. The detector (1) preferably detects the interference signal generated by the above-mentioned sample light and reference light.

The detector (1) is preferably a differential light detector. The detector (1) may also have the function of amplifying the signal. In addition, an amplifier may be provided separately.

The OCT device of the present invention preferably further includes a coupler (also referred to as a coupler (1)) that splits the light from the above-mentioned light source into the split light 1 for generating the above-mentioned sample light and reference light, and Split light 2 used to remove the DC component of the interference signal. The coupler (1) is preferably disposed on the optical path between the above-mentioned light source and the above-mentioned objective lens, and more preferably is disposed on the optical path between the above-mentioned light source and the above-mentioned circulator.

When the coupler (1) is provided, the intensity ratio of the split light 1 and the split light 2 is preferably 90:10 to 99:1, more preferably 92:8 to 98:2. By dividing into such intensity ratios, the DC component can be effectively removed from the interference signal.

The OCT device of the present invention preferably further includes a detector (also referred to as detector (2)) for detecting the divided light 2. The detector (2) may be the same detector as the above-mentioned detector (1), or may be a different detector.

The OCT device of the present invention preferably further includes an attenuator for attenuating the split light 2 . As the attenuator, a variable optical attenuator (VOA) is preferred. The above-mentioned attenuator is preferably arranged on the optical path between the above-mentioned coupler (1) and the detector (2) that detects the split light 2.

The OCT device of the present invention is preferably further equipped with a data acquisition (DAQ) device that collects interference signals generated by the sample light and reference light. The above DAQ device preferably includes an A/D converter. The above DAQ device preferably converts the collected interference signals into digital data.

The OCT device of the present invention preferably further includes a de-aliasing filter (also called a low-pass filter) that attenuates unnecessary frequency components exceeding the measurable distance (Z _max ). The above-mentioned de-aliasing filter is preferably disposed on the optical path between the above-mentioned detector (1) and the above-mentioned DAQ device.

The OCT device of the present invention preferably further includes a computing device that generates an optical interference tomographic image based on the interference signal of the sample light and the reference light. The above-mentioned computing device images the interference signal based on characteristics such as intensity, thereby generating an optical interference tomographic image.

The OCT device of the present invention is preferably further provided with a display device that displays the obtained optical interference tomographic image. The above-mentioned display device may be a fixed type or a portable type, but a portable type is preferred because the image can be confirmed at the shooting site. In addition, the connection with the above-mentioned computing device may be wired or wireless. There may be one display device or a plurality of display devices.

An example of the OCT device of the present invention is shown in FIG. 2 , but the OCT device of the present invention is not limited thereto. In the OCT device 100 of FIG. 2 , the frequency scanning light source 101 outputs the light used for OCT. The frequency scanning light source 101 outputs a trigger signal each time frequency scanning is started. In addition, the light is detected by a Mach-Zehnder interferometer, and a K clock signal for sampling at equal frequency intervals is output. The light output from the frequency scanning light source 101 is split in the coupler 102 at an intensity ratio of 95:5 into split light 1 used to generate the sample light and reference light, and split light used to remove the DC component of the interference signal. 2. Split light 1 is input to port 1 of the circulator 103 and output from port 2, and is transmitted to the detector 104 through an optical fiber of several meters in length. In the detector 104, the split light 1 is converted into parallel light by the collimator 105, is reflected by the galvanometer mirror 106, and is incident on the Fθ lens, that is, the objective lens 107. The galvanometer mirror 106 is driven by the galvanometer mirror driver 111 to scan the parallel light in the XY direction perpendicular to the optical axis. The parallel light incident on the objective lens 107 passes through the reference member 108 and is focused on the sample 110 which is the imaging object, and is reflected on the sample surface and enters the objective lens 107 as sample light. In addition, part of the parallel light incident on the objective lens 107 is reflected on the reference surface 109 of the reference member 108 and enters the objective lens 107 as reference light. The sample light and reference light incident on the objective lens 107 pass through the galvanometer mirror 106 and the collimator 105, then are input to port 2 of the circulator 103 through the optical fiber and output from port 3, and then input to the differential light detection amplifier 113 . The differential light detection amplifier 113 detects and amplifies an interference signal based on the interference of the sample light and the reference light. The split light 2 split by the coupler 102 is attenuated by the variable optical attenuator 112 and then input to the differential light detection amplifier 113 . The differential light detection amplifier 113 uses the signal of the split light 2 to remove the DC component contained in the interference signal. The DC component is removed by the differential light detection amplifier 113, and the amplified interference signal is collected by the DAQ device (A/D converter) provided by the PC 114 and converted into digital data. The collection of interference signals starts according to the trigger signal sent by the frequency scanning light source 101, and is performed synchronously with the K clock signal. Furthermore, a de-aliasing filter (not shown) that attenuates unnecessary frequency components exceeding a measurable distance (Z _max ) is provided between the differential light detection amplifier 113 and the DAQ device. The computing device provided by the PC 114 generates an optical interference tomographic image of the sample 110 based on the interference signal converted by the DAQ device, and displays it on the mobile display 115 .

The OCT device of the present invention is preferably configured in such a manner that a user can carry the part equipped with the objective lens and perform the tomography. Even when the part equipped with the objective lens is made portable in this way, the OCT device of the present invention does not cause environmental differences between the sample optical path and the reference optical path, so the deviation of the tomographic image obtained is small.

The part provided with the objective lens preferably further includes the reference surface (or reference member), the collimator, and the scanning mirror. The part equipped with the above-mentioned objective lens is preferably a detector of an OCT device.

The OCT device of the present invention is preferably configured in such a manner that a user can hold the part equipped with the objective lens to perform the tomography; more preferably, it is configured in a manner that the user can hold the part equipped with the objective lens with one hand to perform the tomography. Photography.

In addition to the above-mentioned objective lens part, the OCT device of the present invention may also have a part that can be carried by the user during tomography. Examples of this part include a driving device for driving the scanning mirror or the display device.

In the OCT device of the present invention, it is preferable that the carried part equipped with the objective lens and the non-carried part are connected through optical fibers, and the light from the above-mentioned light source, the above-mentioned sample light and the reference light are transmitted through the above-mentioned optical fibers. In this aspect, even when the imaging subject is located far away from the non-carrying part, tomography can be performed by adjusting the length of the optical fiber so that the part equipped with the objective lens is close to the imaging subject. The light from the above-mentioned light source, as well as the above-mentioned sample light and reference light are all transmitted through the above-mentioned optical fiber. Therefore, even if the above-mentioned optical fiber is lengthened, there will be no environmental difference between the sample optical path and the reference optical path, and the obtained The deviation of the tomographic image is small. In addition, since it is a wired type using the above-mentioned optical fiber, high-resolution OCT measurement can be performed even on the imaging subject located at a location far away from the above-mentioned non-carrying part.

The length of the optical fiber is not particularly limited and can be determined according to the location of the photographic object. For example, it can be 1 m or more, preferably 3 m or more, more preferably 5 m or more, and still more preferably 10 m or more. Moreover, it may be 100 m or less, or it may be 50 m or less.

The non-portable part preferably includes, for example, the light source, the circulator, the detector, the DAQ device, the arithmetic device, and the like. The above-mentioned non-portable part is preferably the OCT device body (casing).

In the case where there is a portable part in addition to the part equipped with the above-mentioned objective lens, the connection between the part and the part equipped with the above-mentioned objective lens or the above-mentioned non-portable part is not necessarily limited to the connection through an optical fiber, and may also be through a wire, for example. connection.

In the OCT device of the present invention, it is preferable that the length of the optical fiber is 3 m or more, and the temperature difference between the surrounding environment of the portable part equipped with the objective lens and the surrounding environment of the non-carried part is 1°C or more. The deviation of the optical interference tomography image is less than 100 μm. In the industrial field, etc., there are cases where the photographic subject is located far away from the OCT device body (casing), outdoors, or in a facility with high or low temperature. In this case, there will be a big difference in the environment (temperature) between the detector and the OCT device body. Therefore, in an OCT device in which the sample optical path is located on the detector side and the reference optical path is located on the body side, the difference between the sample optical path and the reference optical path is Environmental differences will lead to large deviations in the obtained tomographic images. In contrast, the OCT device of the present invention does not cause environmental differences between the sample optical path and the reference optical path even in the above-mentioned situation, so the deviation of the obtained tomographic image is small.

The length of the optical fiber in the above aspect is preferably 3 m or more, more preferably 5 m or more, and further preferably 10 m or more. Moreover, it may be 100 m or less, or it may be 50 m or less.

In the above-mentioned aspect, the temperature difference of the above-mentioned environment is preferably 1°C or more, more preferably 5°C or more, and further preferably 10°C or more. Moreover, it is preferable that the said temperature difference is 50 degreeC or less.

The deviation of the optical interference tomography image is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less. The above deviation (ΔZ) is specified by the following formula (A): ΔZ (μm) = dn/dT (1/℃) × L (m) × 10 ⁶ × 2 × Δt (℃) (A) (where, dn/dT represents the temperature coefficient of the refractive index of the optical fiber material (1/°C), L represents the length of the optical fiber (m), and Δt represents the temperature difference between the sample optical path and the reference optical path (°C)). The above ΔZ is the deviation of the optical distance. When the fiber material is quartz glass, the wavelength of light is 1.3 μm, and the temperature is close to room temperature, dn/dT is approximately 1.9×10 ^-5 (1/℃).

In an OCT device in which the sample optical path is located on the detector side and the reference optical path is located on the main body side, the temperature difference between the surrounding environment of the part that carries the objective lens and the part that does not carry it is almost directly reflected in the temperature difference in the optical path. Δt, so the deviation ΔZ of the obtained tomographic image is large. On the other hand, in the OCT device of the present invention, even when there is a large temperature difference between the surrounding environment of the part where the objective lens is carried and the part where it is not carried, the temperature difference Δt in the optical path is extremely small, so ΔZ Also extremely small.

Another example of the OCT device of the present invention (an example in which the part equipped with the objective lens is made portable) is shown in FIG. 3 , but the OCT device of the present invention is not limited to this. In FIG. 3 , a user 201 holds the detector 202 of the OCT device with one hand and places the galvanometer mirror driver 205 used to drive the galvanometer mirror built in the detector 202 on his waist. The detector 202 is connected to the housing 206 of the OCT device via an optical fiber 203 . The galvanometer mirror driver 205 is connected to the detector 202 and the housing 206 via a wire 204 . The housing 206 houses a light source, a detector, a DAQ device, a computing device, and the like.

The OCT device of the present invention is preferably configured in such a way that the area in the plane direction that can be photographed with a resolution of 10 μm or more is 0.1 to 14 mm long and 0.1 wide each time a tomography is performed using the following light source. ~14 mm range. This enables high-precision tomography of a wide range at once (even when using other light sources). (light source) AXSUN's high-speed wavelength scanning light source (center wavelength: 1310 nm; scan width: 100 nm; A-scan rate: 50 kHz; output: 25 mW; coherence length: 12 mm)

Using the OCT device of the present invention, optical interference tomography of a sample can be performed. The present invention also relates to an optical interference tomography method using the OCT device of the present invention. In the optical interference tomography method of the present invention, even when the user carries a part (such as a detector) equipped with the above-mentioned objective lens and performs tomography, there will be no environmental difference between the sample optical path and the reference optical path. Therefore, The deviation of the obtained tomographic image is small. In addition, tomography can be performed on a wide range at once.

The OCT device of the present invention has nothing to do with the field of optical interference tomography, and can be suitably used in all optical interference tomography. As described above, even when part of the OCT device is made portable, deviations in tomographic images are less likely to occur, and tomography of a wide range can be performed at once. Therefore, it is particularly suitable for use in the industrial field. use. [Example]

Next, the present invention will be described in further detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Using an OCT device having the structure shown in Figure 2, OCT imaging was performed from the PFA layer side of a fluororesin sheet with a thickness of 7.8 mm, a length of 25 mm, and a width of 25 mm. The above fluororesin sheets were laminated in sequence. 3.1 mm thick polytetrafluoroethylene (PTFE) layer, 0.4 mm thick tetrafluoroethylene/hexafluoropropylene copolymer (FEP) layer and 4.3 mm thick tetrafluoroethylene/perfluoro (alkyl vinyl ether) copolymer (PFA) layer. The obtained tomographic image (length 8 mm × width 8 mm) is shown in Figure 4. Details of the OCT device used and photography conditions are shown below. Scanning laser light source for OCT: central wavelength: 1310 nm; scan width: 100 nm; A-scan rate: 50 kHz; output: 25 mW; coherence length: 12 mm Objective: Fθ lens (trade name: LSM04 manufactured by Thorlabs) ), effective wavelength range (1250~1380 nm), effective focus distance (54 mm) Reference component: quartz glass, cylindrical shape, diameter 20 mm , length 20 mm Optical fiber: made of quartz glass, length 10 m Photography temperature: 26°C Distance between reference surface and sample: 0 cm Other photography conditions: brightness 100, contrast 30

Comparative example 1 It is the same as Example 1 except that the objective lens is changed to an achromatic lens other than an Fθ lens (trade name: AC254-050-C manufactured by Thorlabs; effective wavelength range: 1050 to 1700 nm; effective focal length: 50 mm). method for OCT photography. The obtained cross-sectional image (length 8 mm × width 8 mm) is shown in Figure 5.

In Figure 4, the overall tomographic image is clear and uniform. In contrast, in Figure 5, there is a lot of noise outside the part enclosed by the dotted line, indicating that the effective field of view is narrow (wide-range tomography cannot be completed).

Comparative example 2 An OCT device with the structure shown in Figure 1 was used, and only the optical fiber of the sample arm was heated to 40°C by a dryer, and then OCT photography was performed in the cross-sectional direction of a fluororesin tube with an outer diameter of 12 mm and an inner diameter of 8 mm. The obtained tomographic image is shown in Figure 6 . Details of the OCT device used and photography conditions are shown below. Scanning laser light source for OCT: central wavelength: 1310 nm; scan width: 100 nm; A-scan rate: 50 kHz; output: 25 mW; coherence length: 12 mm Objective lens: Fθ lens (trade name: LSM03 manufactured by Thorlabs), effective wavelength range (1250~1380 nm), effective focus distance (36 mm) Optical fiber (sample arm, reference arm): made of quartz glass, length 4 m Photography temperature: 26℃ Other photography conditions: brightness 100, contrast 30

Reference example 1 OCT imaging was performed in the same manner as in Comparative Example 2 except that the optical fiber of the sample arm was not heated. The obtained tomographic image is shown in Figure 7 .

In Figure 6 where a temperature difference is generated between the arms, the tomographic image of the tube is shifted upward by more than 2 mm in the depth direction compared to Figure 7, and the portion corresponding to the surface of the tube is outside the frame. In addition, artifacts caused by reflection noise (the image of an inverse arc in the upper part of the image) are also seen in Figure 6.

10:OCT device 11:Light source 12,17:Coupler 13,15: Circulator 14: Reference mirror 16:Sample 18:Light detector ①,②,③:port 100:OCT device 101: Frequency scanning light source 102:Coupler 103: Circulator 104:Detector 105:Collimator 106: Galvanometer mirror 107:Objective lens 108:Reference component 109:Reference surface 110:Sample 111: Galvanometer mirror driver 112:Variable optical attenuator 113: Differential light detection amplifier 114:PC 115:Mobile monitor 201:User 202:Detector 203:Optical fiber 204:Wire 205: Galvanometer mirror driver 206: Shell

[Fig. 1] is a schematic diagram showing an example of a conventional optical interference tomography (OCT) apparatus. [Fig. 2] is a schematic diagram showing an example of the OCT device of the present invention. [Fig. 3] is a schematic diagram showing another example of the OCT device of the present invention. [Fig. 4] A diagram showing an OCT image obtained in Example 1. [Fig. 5] A diagram showing an OCT image obtained in Comparative Example 1. [Fig. 6] A diagram showing an OCT image obtained in Comparative Example 2. [Fig. 7] A diagram showing an OCT image obtained in Reference Example 1.

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:port

100:OCT device

101: Frequency scanning light source

102:Coupler

103: Circulator

104:Detector

105:Collimator

106: Galvanometer mirror

107:Objective lens

108:Reference component

109:Reference surface

110:Sample

111: Galvanometer mirror driver

112:Variable optical attenuator

113: Differential light detection amplifier

114:PC

115:Mobile monitor

Claims (10)

An optical interference tomography (OCT) device is provided with an objective lens that focuses light from a light source on a sample, a scanning mirror that scans the light from the light source that is focused on the sample, and a coupler, and is based on The interference of the reflected light from the above-mentioned sample, that is, the sample light, and the reflected light from the reference surface provided between the above-mentioned objective lens and the above-mentioned sample, that is, the reference light, performs tomography of the above-mentioned sample, and the above-mentioned sample light and Both reference lights pass through the above-mentioned objective lens. The above-mentioned objective lens is an Fθ lens. The light from the above-mentioned light source is light with a central wavelength of 1100±50nm, 1310±50nm or 1550±100nm. The above-mentioned reference plane satisfies the following relational expression (3) : n×WD>nd>n×Z _max (3) (where n represents the refractive index of the reference member, WD represents the operating distance of the OCT device, nd represents the optical thickness of the reference member, and Z _max represents the following relational expression (2): Z _max =c/(4δf) (2) (where c represents the speed of light, δf represents the frequency interval of OCT interference signal sampling) represents the measurable distance) of the reference member, the above-mentioned coupling The device splits the light from the above-mentioned light source into the split light 1 used to generate the above-mentioned sample light and reference light, and the split light 2 used to remove the DC component of the interference signal, and the intensity ratio of the split light 1 and the split light 2 is 90:10~99:1. The optical interference tomography apparatus according to claim 1 is configured in such a manner that the tomography can be performed with the distance between the reference surface and the sample being 0 to 3 cm. The optical interference tomography device of claim 1 or 2, wherein the reference plane is a plane of a reference member, and the reference member includes at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz and sapphire. . The optical interference tomography device of claim 1 or 2, wherein both the sample light and the reference light are generated from the light from the light source passing through the objective lens. The optical interference tomography device of claim 1 or 2, wherein the above-mentioned interference is a Festo-type interference. The optical interference tomography device of claim 1 or 2 further includes a circulator that outputs the light from the above-mentioned light source to the side of the above-mentioned objective lens, and outputs the above-mentioned sample light and reference light that pass through the above-mentioned objective lens. to the side of the detector that detects the sample light and reference light. The optical interference tomography device according to claim 1 or 2 is configured in such a way that a user can carry the part equipped with the objective lens and perform the tomography. An optical interference tomography device according to Claim 7, which connects a carrying part equipped with the objective lens and a non-carrying part via an optical fiber, and the light from the above-mentioned light source, the above-mentioned sample light and the reference light are transmitted through the above-mentioned optical fiber. The optical interference tomography device according to claim 8, wherein the length of the optical fiber is 3 m or more, and the temperature difference between the surrounding environment of the portable part with the objective lens and the surrounding environment of the non-carried part is 1°C or more. When, the deviation of the obtained optical interference tomography image is less than 100 μm. An optical interference tomography method using the optical interference tomography device according to any one of claims 1 to 9.